<!DOCTYPE html>



  


<html class="theme-next muse use-motion" lang="zh-Hans">
<head>
  <meta charset="UTF-8"/>
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1"/>
<meta name="theme-color" content="#222">









<meta http-equiv="Cache-Control" content="no-transform" />
<meta http-equiv="Cache-Control" content="no-siteapp" />
















  
  
  <link href="/blog/lib/fancybox/source/jquery.fancybox.css?v=2.1.5" rel="stylesheet" type="text/css" />







<link href="/blog/lib/font-awesome/css/font-awesome.min.css?v=4.6.2" rel="stylesheet" type="text/css" />

<link href="/blog/css/main.css?v=5.1.4" rel="stylesheet" type="text/css" />


  <link rel="apple-touch-icon" sizes="180x180" href="/blog/images/apple-touch-icon-next.png?v=5.1.4">


  <link rel="icon" type="image/png" sizes="32x32" href="/blog/images/favicon-32x32-next.png?v=5.1.4">


  <link rel="icon" type="image/png" sizes="16x16" href="/blog/images/favicon-16x16-next.png?v=5.1.4">


  <link rel="mask-icon" href="/blog/images/logo.svg?v=5.1.4" color="#222">





  <meta name="keywords" content="Hexo, NexT" />










<meta name="description" content="1.引言　相信用过苹果手机的童鞋，会发现很多新闻类的应用，都可以实现HTML图片本地预览，那么这是如何实现的呢？本文将深入阐述其中的原理. 　　关于此功能，我还实现了一个DEMO，大家可以点击此访问更详细内容　　 　　　 　 　　　 2.原理  接触过web开发的人，就了解与html元素交互都是通过javascript进行的，比如点击、滑动等，比如点击标签的响应代码如下  var img = do">
<meta property="og:type" content="article">
<meta property="og:title" content="iOS HTML图片本地预览">
<meta property="og:url" content="http://smallmuou.gitee.io/blog/2015/07/29/2015-07-29-iOS HTML图片本地预览/index.html">
<meta property="og:site_name" content="smallmuou&#39;s blog">
<meta property="og:description" content="1.引言　相信用过苹果手机的童鞋，会发现很多新闻类的应用，都可以实现HTML图片本地预览，那么这是如何实现的呢？本文将深入阐述其中的原理. 　　关于此功能，我还实现了一个DEMO，大家可以点击此访问更详细内容　　 　　　 　 　　　 2.原理  接触过web开发的人，就了解与html元素交互都是通过javascript进行的，比如点击、滑动等，比如点击标签的响应代码如下  var img = do">
<meta property="og:locale" content="zh-Hans">
<meta property="og:image" content="http://images0.cnblogs.com/blog2015/618689/201507/281746477031029.png">
<meta property="og:image" content="http://images0.cnblogs.com/blog2015/618689/201507/281746583287949.png">
<meta property="og:updated_time" content="2020-04-16T01:15:21.879Z">
<meta name="twitter:card" content="summary">
<meta name="twitter:title" content="iOS HTML图片本地预览">
<meta name="twitter:description" content="1.引言　相信用过苹果手机的童鞋，会发现很多新闻类的应用，都可以实现HTML图片本地预览，那么这是如何实现的呢？本文将深入阐述其中的原理. 　　关于此功能，我还实现了一个DEMO，大家可以点击此访问更详细内容　　 　　　 　 　　　 2.原理  接触过web开发的人，就了解与html元素交互都是通过javascript进行的，比如点击、滑动等，比如点击标签的响应代码如下  var img = do">
<meta name="twitter:image" content="http://images0.cnblogs.com/blog2015/618689/201507/281746477031029.png">



<script type="text/javascript" id="hexo.configurations">
  var NexT = window.NexT || {};
  var CONFIG = {
    root: '/blog/',
    scheme: 'Muse',
    version: '5.1.4',
    sidebar: {"position":"left","display":"post","offset":12,"b2t":false,"scrollpercent":false,"onmobile":false},
    fancybox: true,
    tabs: true,
    motion: {"enable":true,"async":false,"transition":{"post_block":"fadeIn","post_header":"slideDownIn","post_body":"slideDownIn","coll_header":"slideLeftIn","sidebar":"slideUpIn"}},
    duoshuo: {
      userId: '0',
      author: '博主'
    },
    algolia: {
      applicationID: '',
      apiKey: '',
      indexName: '',
      hits: {"per_page":10},
      labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}
    }
  };
</script>



  <link rel="canonical" href="http://smallmuou.gitee.io/blog/2015/07/29/2015-07-29-iOS HTML图片本地预览/"/>





  <title>iOS HTML图片本地预览 | smallmuou's blog</title>
  








</head>

<body itemscope itemtype="http://schema.org/WebPage" lang="zh-Hans">

  
  
    
  

  <div class="container sidebar-position-left page-post-detail">
    <div class="headband"></div>

    <header id="header" class="header" itemscope itemtype="http://schema.org/WPHeader">
      <div class="header-inner"><div class="site-brand-wrapper">
  <div class="site-meta ">
    

    <div class="custom-logo-site-title">
      <a href="/blog/"  class="brand" rel="start">
        <span class="logo-line-before"><i></i></span>
        <span class="site-title">smallmuou's blog</span>
        <span class="logo-line-after"><i></i></span>
      </a>
    </div>
      
        <p class="site-subtitle"><a href="https://github.com/smallmuou">https://github.com/smallmuou</a></p>
      
  </div>

  <div class="site-nav-toggle">
    <button>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
    </button>
  </div>
</div>

<nav class="site-nav">
  

  
    <ul id="menu" class="menu">
      
        
        <li class="menu-item menu-item-home">
          <a href="/blog/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-home"></i> <br />
            
            首页
          </a>
        </li>
      
        
        <li class="menu-item menu-item-archives">
          <a href="/blog/archives/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-archive"></i> <br />
            
            归档
          </a>
        </li>
      
        
        <li class="menu-item menu-item-categories">
          <a href="/blog/categories/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-th"></i> <br />
            
            分类
          </a>
        </li>
      
        
        <li class="menu-item menu-item-about">
          <a href="/blog/about/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-user"></i> <br />
            
            关于
          </a>
        </li>
      

      
    </ul>
  

  
</nav>



 </div>
    </header>

    <main id="main" class="main">
      <div class="main-inner">
        <div class="content-wrap">
          <div id="content" class="content">
            

  <div id="posts" class="posts-expand">
    

  

  
  
  

  <article class="post post-type-normal" itemscope itemtype="http://schema.org/Article">
  
  
  
  <div class="post-block">
    <link itemprop="mainEntityOfPage" href="http://smallmuou.gitee.io/blog/blog/2015/07/29/2015-07-29-iOS HTML图片本地预览/">

    <span hidden itemprop="author" itemscope itemtype="http://schema.org/Person">
      <meta itemprop="name" content="smallmuou">
      <meta itemprop="description" content="">
      <meta itemprop="image" content="/blog/images/avatar.gif">
    </span>

    <span hidden itemprop="publisher" itemscope itemtype="http://schema.org/Organization">
      <meta itemprop="name" content="smallmuou's blog">
    </span>

    
      <header class="post-header">

        
        
          <h1 class="post-title" itemprop="name headline">iOS HTML图片本地预览</h1>
        

        <div class="post-meta">
          <span class="post-time">
            
              <span class="post-meta-item-icon">
                <i class="fa fa-calendar-o"></i>
              </span>
              
                <span class="post-meta-item-text">发表于</span>
              
              <time title="创建于" itemprop="dateCreated datePublished" datetime="2015-07-29T00:00:00+08:00">
                2015-07-29
              </time>
            

            

            
          </span>

          
            <span class="post-category" >
            
              <span class="post-meta-divider">|</span>
            
              <span class="post-meta-item-icon">
                <i class="fa fa-folder-o"></i>
              </span>
              
                <span class="post-meta-item-text">分类于</span>
              
              
                <span itemprop="about" itemscope itemtype="http://schema.org/Thing">
                  <a href="/blog/categories/IOS/" itemprop="url" rel="index">
                    <span itemprop="name">IOS</span>
                  </a>
                </span>

                
                
              
            </span>
          

          

          
          

          

          

          

        </div>
      </header>
    

    
    
    
    <div class="post-body" itemprop="articleBody">

      
      

      
        <h2 id="1-引言"><a href="#1-引言" class="headerlink" title="1.引言"></a>1.引言</h2><p>　相信用过苹果手机的童鞋，会发现很多新闻类的应用，都可以实现HTML图片本地预览，那么这是如何实现的呢？本文将深入阐述其中的原理.</p>
<p>　　关于此功能，我还实现了一个DEMO，大家可以点击此<a href="https://github.com/smallmuou/PPHTMLImagePreviewDemo" target="_blank" rel="noopener">访问更详细内容</a><br>　　<br><br> 　<img src="http://images0.cnblogs.com/blog2015/618689/201507/281746477031029.png" alt="image"><br>　　<img src="http://images0.cnblogs.com/blog2015/618689/201507/281746583287949.png" alt="image">
　
　　　</p>
<h2 id="2-原理"><a href="#2-原理" class="headerlink" title="2.原理"></a>2.原理</h2><p>  接触过web开发的人，就了解与html元素交互都是通过javascript进行的，比如点击、滑动等，比如点击<img>标签的响应代码如下<br>  <pre><br>var img = document.getElementById(‘test’);<br>img.onclick = function() {<br>    do some thing<br>}<br>  </pre></p>
<p>  顺着这个思路往下想，就可以推测出，在iOS中实现点击图片本地预览，也应该是跟javascript交互的，于是问题转换成了javascript与objc的交互. 关于javascript与objc的交互，google下一大堆，看似很复杂，其实非常简单，我这里简单阐述下，大家都知道在iOS中是用UIWebView控件来显示HTML的，那么javascript与objc要实现交互，桥梁必须是UIWebView，通过查看UIWebView提供的相关接口，可以找到如下接口:</p>
<pre>
- (NSString *)stringByEvaluatingJavaScriptFromString:(NSString *)script
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType;
</pre>

<p>第一个接口一目了然，即执行javascript，于是就打通了objc到javacript的路，那么javascript到objc呢？答案就是第二个接口，因为当html点击一个新链接就会执行该接口来判定是否要进入新链接，于是只有让javascript去改变href从而来触发第二个接口的调用，就能打通了javascript到objc的路，参数当然存放于request的href中。</p>
<p>　　在了解了javascript与objc的交互，还有一个小问题，即何时去执行javascript？查看UIWebView文档，发现可以在如下接口中调用</p>
<pre>
- (void)webViewDidFinishLoad:(UIWebView *)webView;
</pre>

<h2 id="3-实现"><a href="#3-实现" class="headerlink" title="3. 实现"></a>3. 实现</h2><p>在webViewDidFinishLoad执行如下javascript代码，大致功能是遍历html中所有&lt; img&gt;元素，并添加onclick事件，在onclick中修改window.location.href，以触发UIWebView调用webView:shouldStartLoadWithRequest:navigationType接口，参数是image-preview:+&lt; img&gt;标签的src属性</p>
<pre>
function assignImageClickAction() {
var imgs = document.getElementsByTagName('img');
var length = imgs.length;
for (var i = 0; i < length; i++) {
    img = imgs[i];
    img.onclick = function() {
        window.location.href = 'image-preview:' + this.src
    }
}
}
assignImageClickAction();
</pre>

<p>上述javascript可以通过压缩，实际代码如下</p>
<pre>
- (void)webViewDidFinishLoad:(UIWebView *)webView {
    [self.webView stringByEvaluatingJavaScriptFromString:@"function assignImageClickAction(){var imgs=document.getElementsByTagName('img');var length=imgs.length;for(var i=0;i < length;i++){img=imgs[i];img.onclick=function(){window.location.href='image-preview:'+this.src}}}"];
    [self.webView stringByEvaluatingJavaScriptFromString:@"assignImageClickAction();"];
}
</pre>

<p>当用户点击<img>会触发如下代码</p>
<pre>
- (BOOL)webView:(UIWebView *)webView shouldStartLoadWithRequest:(NSURLRequest *)request navigationType:(UIWebViewNavigationType)navigationType {
    //预览图片
    if ([request.URL.scheme isEqualToString:@"image-preview"]) {
        NSString* path = [request.URL.absoluteString substringFromIndex:[@"image-preview:" length]];
        path = [path stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
        [self.imageView setImageWithURL:[NSURL URLWithString:path] placeholderImage:[UIImage imageNamed:@"default"] usingActivityIndicatorStyle:UIActivityIndicatorViewStyleWhite];

        [UIView animateWithDuration:0.2f animations:^{
            self.imageView.alpha = 1.0f;
        }];

        return NO;
    }
    return YES;
}
</pre>

<h2 id="综述"><a href="#综述" class="headerlink" title="综述"></a>综述</h2><p>至此，大家应该明白了iOS APP点击HTML实现本地预览的原理，当然这仅仅只是个开始，你可以修改window.location.href传递的值，从而实现更多功能，比如小图、大图预览等，大家可以到<a href="https://github.com/smallmuou/PPHTMLImagePreviewDemo" target="_blank" rel="noopener">这里下载源码](访问更详细内容</a>.</p>

      
    </div>
    
    
    

    

    

    

    <footer class="post-footer">
      

      
      
      

      
        <div class="post-nav">
          <div class="post-nav-next post-nav-item">
            
              <a href="/blog/2015/07/27/2015-07-27-ObjC转向Swift若干tips/" rel="next" title="ObjC转向Swift若干tips">
                <i class="fa fa-chevron-left"></i> ObjC转向Swift若干tips
              </a>
            
          </div>

          <span class="post-nav-divider"></span>

          <div class="post-nav-prev post-nav-item">
            
              <a href="/blog/2015/10/09/2015-10-09-ObjC之Block解读/" rel="prev" title="ObjC之Block解读">
                ObjC之Block解读 <i class="fa fa-chevron-right"></i>
              </a>
            
          </div>
        </div>
      

      
      
    </footer>
  </div>
  
  
  
  </article>



    <div class="post-spread">
      
    </div>
  </div>


          </div>
          


          

        </div>
        
          
  
  <div class="sidebar-toggle">
    <div class="sidebar-toggle-line-wrap">
      <span class="sidebar-toggle-line sidebar-toggle-line-first"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-middle"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-last"></span>
    </div>
  </div>

  <aside id="sidebar" class="sidebar">
    
    <div class="sidebar-inner">

      

      
        <ul class="sidebar-nav motion-element">
          <li class="sidebar-nav-toc sidebar-nav-active" data-target="post-toc-wrap">
            文章目录
          </li>
          <li class="sidebar-nav-overview" data-target="site-overview-wrap">
            站点概览
          </li>
        </ul>
      

      <section class="site-overview-wrap sidebar-panel">
        <div class="site-overview">
          <div class="site-author motion-element" itemprop="author" itemscope itemtype="http://schema.org/Person">
            
              <p class="site-author-name" itemprop="name">smallmuou</p>
              <p class="site-description motion-element" itemprop="description"></p>
          </div>

          <nav class="site-state motion-element">

            
              <div class="site-state-item site-state-posts">
              
                <a href="/blog/archives/">
              
                  <span class="site-state-item-count">197</span>
                  <span class="site-state-item-name">日志</span>
                </a>
              </div>
            

            
              
              
              <div class="site-state-item site-state-categories">
                <a href="/blog/categories/index.html">
                  <span class="site-state-item-count">12</span>
                  <span class="site-state-item-name">分类</span>
                </a>
              </div>
            

            

          </nav>

          

          
            <div class="links-of-author motion-element">
                
                  <span class="links-of-author-item">
                    <a href="https://github.com/smallmuou" target="_blank" title="GitHub">
                      
                        <i class="fa fa-fw fa-globe"></i>GitHub</a>
                  </span>
                
            </div>
          

          
          

          
          

          

        </div>
      </section>

      
      <!--noindex-->
        <section class="post-toc-wrap motion-element sidebar-panel sidebar-panel-active">
          <div class="post-toc">

            
              
            

            
              <div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-2"><a class="nav-link" href="#1-引言"><span class="nav-number">1.</span> <span class="nav-text">1.引言</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#2-原理"><span class="nav-number">2.</span> <span class="nav-text">2.原理</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#3-实现"><span class="nav-number">3.</span> <span class="nav-text">3. 实现</span></a></li><li class="nav-item nav-level-2"><a class="nav-link" href="#综述"><span class="nav-number">4.</span> <span class="nav-text">综述</span></a></li></ol></div>
            

          </div>
        </section>
      <!--/noindex-->
      

      

    </div>
  </aside>


        
      </div>
    </main>

    <footer id="footer" class="footer">
      <div class="footer-inner">
        <div class="copyright">&copy; <span itemprop="copyrightYear">2020</span>
  <span class="with-love">
    <i class="fa fa-user"></i>
  </span>
  <span class="author" itemprop="copyrightHolder">smallmuou</span>

  
</div>

    <script async src="https://busuanzi.ibruce.info/busuanzi/2.3/busuanzi.pure.mini.js"></script>

    <span id="busuanzi_container_site_pv">总访问量<span id="busuanzi_value_site_pv"></span>次</span>
    <span class="post-meta-divider">|</span>



  <div class="powered-by">由 <a class="theme-link" target="_blank" href="https://hexo.io">Hexo</a> 强力驱动</div>



  <span class="post-meta-divider">|</span>



  <div class="theme-info">主题 &mdash; <a class="theme-link" target="_blank" href="https://github.com/iissnan/hexo-theme-next">NexT.Muse</a> v5.1.4</div>




        







        
      </div>
    </footer>

    
      <div class="back-to-top">
        <i class="fa fa-arrow-up"></i>
        
      </div>
    

    

  </div>

  

<script type="text/javascript">
  if (Object.prototype.toString.call(window.Promise) !== '[object Function]') {
    window.Promise = null;
  }
</script>









  












  
  
    <script type="text/javascript" src="/blog/lib/jquery/index.js?v=2.1.3"></script>
  

  
  
    <script type="text/javascript" src="/blog/lib/fastclick/lib/fastclick.min.js?v=1.0.6"></script>
  

  
  
    <script type="text/javascript" src="/blog/lib/jquery_lazyload/jquery.lazyload.js?v=1.9.7"></script>
  

  
  
    <script type="text/javascript" src="/blog/lib/velocity/velocity.min.js?v=1.2.1"></script>
  

  
  
    <script type="text/javascript" src="/blog/lib/velocity/velocity.ui.min.js?v=1.2.1"></script>
  

  
  
    <script type="text/javascript" src="/blog/lib/fancybox/source/jquery.fancybox.pack.js?v=2.1.5"></script>
  


  


  <script type="text/javascript" src="/blog/js/src/utils.js?v=5.1.4"></script>

  <script type="text/javascript" src="/blog/js/src/motion.js?v=5.1.4"></script>



  
  

  
  <script type="text/javascript" src="/blog/js/src/scrollspy.js?v=5.1.4"></script>
<script type="text/javascript" src="/blog/js/src/post-details.js?v=5.1.4"></script>



  


  <script type="text/javascript" src="/blog/js/src/bootstrap.js?v=5.1.4"></script>



  


  




	





  





  












  





  

  

  

  
  

  

  

  

</body>
</html>
